There have been known various technologies each for backing up an apparatus (a server) which provides service to client terminals.
For example, in Japanese Unexamined Patent Application Publication No. Hei 07-66829, there is disclosed a related technology which backs up an e-mail server by multiplexing a plurality of e-mail servers. In this related technology, each of the plurality of e-mail servers has the function of copying and storing therein the contents of mailboxes included in some of the other ones of the plurality of e-mail servers. Further, a client terminal utilizes e-mail service by accessing one of available ones of the plurality of e-mail servers. Further, even when a fault has occurred in an e-mail server among the plurality of e-mail servers, to which a client terminal has been in a state of making an access, the client terminal can continue to utilize the e-mail service by accessing another available one of the plurality of e-mail servers.
Further, for example, in Japanese Unexamined Patent Application Publication No. 2007-274053, there is disclosed a related technology with respect to a method of performing mirroring of mails from an e-mail server to a backup server. In this related technology, when performing a mail addition or deletion process on mailboxes, the e-mail server creates copying information on a mail-by-mail basis with respect to mails targeted for the mail addition or deletion process. Further, the e-mail server transmits the copying information to the backup server. The backup server performs a mail addition or deletion process on mailboxes of the backup server itself on the basis of the received copying information. In this way, in this related technology, the contents of the mailboxes are kept the same between the e-mail server and the backup server. As a result, in this related technology, even when operation has been switched from the e-mail server to the backup server, it is possible to continuously provide client terminals with the e-mail service.
Further, for example, in Japanese Unexamined Patent Application Publication No. 2006-259945, there is disclosed a related technology which backs up a plurality of cards (corresponding to a plurality of servers) mounted on a radio network controller. In this related technology, the radio network controller includes a spare card and a plurality of cards each providing a corresponding one of processes (services) needed for controlling the wireless network. Each of the cards stores self-data therein, and additionally, stores therein backup data for data stored in any other one of the cards. Further, each of the cards is configured to, when the self-data has been changed, transmit copy data resulting from copying the changed self-data to any other one of the cards which stores therein backup data for the self-data, and cause the any other one of the cards to store therein the copy data as the backup data. Further, in this related technology, when a fault has occurred in one of the cards, the radio network controller continues its processing by copying backup data for data of the faulty card from one of the cards which stores the backup data therein to the spare card, and using this spare card as substitute for the faulty card.